Electrical switch



July 6, 1948. M. PUSTER ELECTRICAL SWITCH Filed April 4, 1947 G i'i'onzegs Patented July 6, 1948 Louis M. Pastor,

Knoxville, Tenn., assignor to Robertshaw-Fulton Controls Companmacorporation of Delaware Application Aprll 4, 1947, Seriai No. 789,428 '7Claims. (Cl. 200-67) This invention relates to electrical switches, andmore particularly to electrical switches of the snap action type.

It is an object of the present invention to provide an improvedelectrical switch of the snap action type which is so constructed as tominimize sparking.

Another object of this invention is to provide an improved snap actionelectrical switch wherein the actuating member may be moved through apredetermined distance without initiating the snap action.

Another object of this invention is to provide an improved snap actionelectrical switch of the type last characterized wherein the snap actionis independent of the speed with which the actuating means is moved.

Another object of an improved snap action electrical switch wherein theinitial movement of the actuating means tends to urge the electricalcontacts together with increased pressure up to the instant the snapaction becomesefiective to separate the contacts abruptly.

Another object of this invention is to provide an improved snap actionelectrical switch which is composed of a minimum number of easilyfabricated parts so that it is inexpensive to produce.

Another object of this invention is to provide an improved snap actionelectrical switch which may be readily adjusted to predetermine thecharacteristics of the snap action.

Other objects will appear as the description of the invention proceeds.

The invention is capable of receiving a variety of mechanicalexpressions, only one of which has been illustrated on the accompanyingdrawings, and it is therefore to be expressly understood that thedrawings are for purposes of illustration only, and are not intended tobe a definition of the limits of the invention, reference being had tothe appended claims for that purpose.v

Referring in detail to said drawings, wherein the same referencecharacters are used to designate corresponding parts in the severalfigures,

Fig. 1 is a perspective elevation of an embodiment of the presentinvention;

Fig. 2 is an enlarged cross section on the line 22 of Fig. 1;

Figs. 3 and 4 are views corresponding to Fig. 2 but illustrating theposition of the parts at different times during the movement of theactuating means; and a Fig. 5 is a cross section on the line 65 of Fig.2.

this invention is toprovide- I her I it and cover it 20 and therebyReferring in detail to the drawings, the parts of the switch are shownas enclosed within a housing of any suitable size, configuration andmaterial, illustrated as comprising a. body memof insulating materialproviding therein a switch chamber l2. Cover i I may be permanentlysecured to the body member it] after the parts are assembled, althoughif preferred provision may be made for rendering the cover detachablefrom the body member to gain access to the parts of the switch.

Mounted on the body member it approximately midwayof its length is anupstanding wedgeshaped fulcrum projection it, and extending downwardlyfrom the cover it is a like projection it so disposed that the apices ofthe two projections are in alignment when the cover i l is in positionon the body member it. Mounted be-. tween said fulcrum projections itand i5 is an elongated leaf spring it of any suitable width, theapicesof said projections engaging the opposite faces of said spring atapproximately the midpoint of its length. At its extremities said springis received in the approximately v-shaped or U- shaped recesses ill andit of a pair of depending brackets is and 20 secured in any suitable wayto the cover i l as by rivets 2|. Leaf spring it has a length such as tobe somewhat longer than the length between the bottoms of the recessesl1 and it so that when said spring is supported at its ends in saidrecesses it must assume a bowed configuration and then, when the coveris installed on the body member so that the aligned apices of theprojections It and i5 engages said spring midway of its length as shownin Fig. 2,

said spring is forced to assume a somewhat sinusoidal form, that is,with one half of the spring bowed upwardly, as shown at '22 in Fig. 2,and the other half bowed downwardly, as shown at 23 in Fig. 2.

Provision is preferably made for adjusting the extent to which the sringit may be bowed, and to this end at least the bracket is is madesumciently resilient so that it may be bent to varying extents, andsuitably mounted in the end wall of the cover It is a short threadedstud or screw 26, rotatable in a nut 25 embedded in the material of thecover, with the inner end of the screw it engaging the socketed end ofthe bracket is so that by adjustment of the screw inwardly or outwardlywith respect to the cover the socketed end of the bracket is may bevaried in position to vary its effective distance from the bracket varythe extent to which the Sprin 48 is hnmnll block is, although has astop,

Mounted on and approximately midway of the section 23 of spring I6 is amovable contact member of any suitable construction, here shown as inthe form of an inverted U-shaped block 26 of any suitable insulatingmaterial (see Fig. attached to the spring IS in any suitable way, as byone or more rivets 21, and having its downwardly extending extremities28 and 29 bridged by a metal piece 30 with further insulation 3|interposed between the bridge member 30 and the the latter may beomitted if desired. In the form here shown, contact member 26 isprovided with one or more suitable contact elements, shown as a pair ofstuds 32 and 33 retained in the member 25 in any suitable way and havingbelow the bridge piece 30 contact heads 34 provided with contactsurfaces 35. Mounted in any suitable way in the body member ID are oneor more suitable opposed stationary contact elements, shown as contacts36 and 31 provided with contact faces 38 in alignment with contact faces35. Each of said stationary contacts 36 and 31 is shown as mounted on ametallic plate 33 suitable way, as by a screw 40 engaging threads on atubular conducting element 4| which extends to the outer face of thebody member In where a contact screw 42 similarly engaged with saidtubular conducting element 41 may be used to secure any suitableelectrical conductor 43 in conductive relationship with the tubularmember 4|. Any other suitable provision for connecting the contactelements with any suitable conduc'torsmay be used if preferred.

Any suitable means may be used for actuating the spring l8. As shown, athrust member 44, which may be opera-ted manually or by any suitableautomatic mechanism, is reciprocatingly mounted in an aperture 45 of thecover and has its inner extremity 46 normally engaged with the section22 of .the spring l6 approximately midway of its length. As here shown,thrust member 44 carries a depending inverted U -shaped bracket 41, andthe downwardly extending legs of said bracket 41 carry a cup-shapedspring retainer 48 that is reciprocatingly mounted in a recess 49 in thebody member Ill. Mounted in said recess 49 between the bottom of saidrecess and said cupshaped spring retainer 48 is a coil spring 50.Cupshaped spring retainer 48 also has-secured thereto an upwardlyextending post 5| in alignment with but somewhat spaced from the thrustmember 44 so that, as shown in Fig. 2, said post 5! is always out ofcontact with the section 22 of spring IE to provide some freedom ofrelative movement until said spring snaps into engagement with said postas shown in Fig. 4. The bottom of recess 49 shown as a circular shoulder52, to limit the downward movement of retainer 48 to that position atwhich the spring l6, now engaged with the end of post 5!, retains thedesired sinusoidal shape.

The parts of the switch are normally in the relative position shown inFig. 2 with the downwardly bowed section 23 of spring l6 holding themovable contact member 26 in such position that contacts 34, 34 arefirmly engaged with the stationary contacts 36 and 31. The upwardlybowed section 22 of spring I6 is in engagement with the inner end of thethrust member 44 but slightly spaced from the upper ehd of the post 54Assuming that the thrust member 44 is to be manually actuated, thrustmember 44 is pushed inwardly when it is desired to open the switch. Thefirst inward movement of thrust member 44 merely secured to the bodymember I0 in any 4 flattens the section 22 of spring It as shown in Fig.3, after which further inward movement of the thrust member 44 pressesthe cup-shaped spring retainer 48 downwardly as viewed in the drawings,moving the retainer inwardly into the recess 49 against the tension ofthe spring 5!] until it is stopped by shoulder 52. The flattening of thesection 22 imposes increased compression on the section 23 of saidspring 18 so as to press the movable contacts into engagement with thestationary contacts withincreased pressure. When the spring section 22by inward movement of the thrust member 44 passes the position shown inFig. 3 in which section 22 is unbowed, the spring l6 instantaneouslysnaps to the condition of opposite curvature shown in Fig. 4 wherein thesection 23 of the spring is bowed upwardly and the section 22 of thespring is bowed downwardly. Thereby the movable contacts are abruptlyseparated from the stationary contacts. The contacts are then retainedin their separated relationship, with the circuit open, as long asthrust member 44 is held in its inward position shown in Fig. 4, inwhich position the coil spring 50 is under compression. Therefore, whenpressure isreleased on the thrust member 44 thesection 22 of the springI6 is moved upwardly as viewed in the drawings by the action of thespring 53 until having passed the flattened relationship shown in Fig. 3the spring I6 again abruptly reverses its direction of curvature,resuming the relationship shown in Fig. 2 and instantaneously moving themovable contacts into contact with the stationary contacts.

By use of a stop shoulder 52 as illustrated the spring retainer 48 isstopped at such a predetermined point as is necessary to bring the part22 of spring ii to rest upon the end surface of the post 5|, buteliminating the possibility of a further inward actuation of the thrustmember 44, which if moved further inward would develop a more inwardbowing of the section 22 of spring 16 that would in turn introduce asomewhat non-sinusoidal curve of the spring l6, whereby the section 23of said spring would have a tendency, under the above condition, tobecome somewhat straight, permitting the contact 34 to move inwardlytoward the stationary contact 36 with the possible danger of causing anundesired arcing effect. Also, as is sometimes the case, if it isdesired to have another contact engaged by a contact on member 26 inthis outward position of the section 23 of spring it, said additionalcontact being suitably located above contact 34, excessive inwardmovement of member 44 would cause varying contact pressure on suchcontact with possibly a false break" of the contact but not enough toeliminate arcing. Furthermore, the use of this shoulder 52 asillustrated is a means of stopping the spring retainer 48 at thatpredetermined point which is necessary to bring the part 22 of spring 15to rest upon the end of the post 5i so as to render the return forcemechanism, including spring 50, retainer 48 and post 5!, capable ofinstantaneous action the moment pressure is released from thrust member44.

It will therefore be perceived that whether the thrust member 44 isactuated manually or by any suitable automatic mechanism the speed atwhich said member 44 is moved is entirely independent of the abruptnesswith which the relatively movable contacts are moved into and out ofengagement with the stationary contacts by the snap action oi thereverseiy bowed spring l6. When.

thrust member 64 is being moved inwardly to the.

flattened relationship of section 22 compression imposed on spring i6 issuch as to press the movable contacts into firmer and firmer contactwith the stationary contacts up to that instant at which the snap actiontakes place, and this in itself has a tendency to minimize sparking. Thespring It may be nicely adjusted by actuation of the screw 24 so as toeffect the desired bowing of the spring It. The switch is composed of arelatively few number of parts all of which Y are easy to fabricate andassemble and therefore a switch in conformity with the present inventioncan be manufactured at minimum expense.

While it is'preferred to embody the invention I in a switch which isactuated automatically when the thrust member M is released, it will beapparent to those skilled in the art that as respects certain featuresof the invention they may be embodied in constructions wherein thespring I6 is moved from one to the other of its extreme positions inboth directions by suitable means extending to the exterior of thehousing and controlled either manually or automatically. Furthermore.while the illustrated embodiment is one wherein the contacts arenormally held,

in closed position and the thrust member 44 is actuated to hold thecontact elements in open position, this relationship can be readilyreversed so that the contact elements are normally retained in openposition and engaged only when thrust elementM is actuated as aboveexplained.-

While the embodiment of the invention illustrated on the drawings hasbeen described with considerable particularity, it is to be expresslyunderstood that the invention is not limited thereto as the same iscapable of receiving a variety of mechanical expressions as will now beapparent to those skilled in the art, while changes may be made indetails of construction, arrange-- ment, proportion of parts, etc.,other provisions may be made-for mounting and connecting the relativelymovable contacts with outside conductors, other means may be used forreturning the spring it to its normal relationship when pressure isreleased on the thrust member M, etc., without departing from the spiritof the present invention. Reference is therefore to be had to theappended claims for a definition of the invention.

What is claimed is:

1. In a snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, meansmountsaid bowed spring sections, at least one stationary contact elementcarried by said housing for cooperation with said movable contactelement, and means cooperating with the other of said bowed springsections approximately midway of its length for reversing the directionof curvature of said last'named section and thereby the direction ofcurvature of said first named section to .move said contact elementswith respect to each other.

2. In a snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, meansmounting said leaf spring at its ends, opposed fulcrum member engagingsaid leaf spring approximately midway of its ,length, the length of saidspring being greater than the distance between said mounting meanswhereby with the cooperation of said fulcrum members said spring 'is'bowed in opposite directions on opposite sides of said fulcrummembers,at least one movable contact element mounted approximately midway of oneof said bowed spring sections, at least one stationary contact elementcarried by said housing for cooperation with said movable contactelement, means cooperating with the other of said bowed spring sectionsapproximately midway of its length for reversing the direction ofcurvature of said last named section and thereby the direction oi.curvature of said first named section to move said contact elements withrespect to each other, and means for adjusting the extent of curvatureof said leaf spring.

3. In a. snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, meansmounting said leaf spring at its ends, opposed fulcrum members engagingsaid leaf spring approximately midway of its length, the length of saidspring being greater than the distance between said mounting meanswhereby with the cooperation of said fulcrum members said spring isbowed in opposite directions on opposite sides of said fulcrum members,at least one movable contact element mounted approximately midway of oneof said bowed spring sections, at least one stationary contact elementcarried by said housing for cooperation with said movable contactelement, means cooperating with the other of said bowed spring sectionsapproximately midway of its length for reversing the direction ofcurvature of said last named section and thereby the direction ofcurvature of said first named section to move said contact elements withrespect to each other, and spring means tensioned by the reversal ofcurvature of said leaf spring for returning said spring to its originalcurvature when pressure is released on said second named spring section.

ing said leaf spring at its ends, opposed fulcrum members engaging saidleaf spring approximately midway of its length, the length of saidspring being greater than the distance between said mounting meanswhereby with the cooperation of said fulcrum members said spring isbowed in opposite directions on opposite sides of said fulcrum members,at least one movable contact element mounted approximately midway of oneof 4. In a snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, bracketsprovided with recesses in which the ends of said spring are mounted,opposed fulcrum members engaging the opposite faces of said springapproximately midway of its length, said spring being of greater lengththan the distance between and thrust means cooperating with other ofsaid spring sections approximately midway of its length and adapted toreverse the direction of therewith.

5.'In a snap action electrical switch, incombination with a housingproviding a switch chamber, a leaf spring in said chamber, bracketsprovided with recesses in which the ends of said spring are mounted,opposed fulcrum members engaging the opposite facesof said springapproximately midway of its length, said sprin being of greater lengththan the distance between. the bottoms of the recesses in said bracketswhereby with the cooperation of said fulcrum members the sections ofsaid spring at opposite sides of said fulcrum members are bowed inopposite directions, a movable contact member mounted on said springapproximately midway of the length of one of said bowed sections,stationary contact means carried by said housing for cooperation withsaid movable contact member, thrust means cooperating with other of saidspring sections approximately midway of its length and adapted toreverse the direction of curvature thereof to thereby reverse thedirection of curvature of the first spring section and move the movablecontact member abruptly with respect to the stationary contact meanswhen said thrust member has moved a predetermined distance to flattenthe spring section associated therewith, and means cooperating with oneof said brackets for flexing the same to vary the distance between thebottoms of the recesses in said brackets.

6. In a snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, bracketsprovided with recesses in which the ends of said spring are mounted,opposed fulcrum members engaging the opposite faces of said springapproximately midway of its length, said spring being or greaterlength'than the distance between the bottoms of the recesses in saidbrackets whereby with the cooperation of said fulcrum members thesections of said spring at opposite sides of said fulcrum members arebowed in opposite directions, a movable contact member mounted on saidspring approximately midway of the length of one of said bowed sections,stationary contact means carried by said housing for cooperation withsaid movable contact member, thrust means cooperating with other of saidspring sections approximately midway of its length and adapted toreverse the direction of curvature thereof to thereby reverse thedirection of curvature of the first spring section and move the movable,contact member abruptly with respect to the stationary contact meanswhen said thrust member has moved a predetermined distance to flattenthe spring section associated therewith, and a spring tensioned by thereversal of fiexure of said second section to restore said secondsection to its "original direction of flexure when pressure is releasedon said thrust member.

7. In a snap action electrical switch, in combination with a housingproviding a switch chamber, a leaf spring in said chamber, meansproviding recesses in which the ends of said spring are mounted, thedistance between the bottoms of said recesses being less than the lengthof said spring, opposed fulcrum members carried by the opposite walls ofsaid chamber and engaging said spring approximately midway of its lengthat opposite faces thereof whereby the sections of said spring atopposite sides of said fulcrum membars are bowed in opposite directions,a movable contact member carried by one of said sections approximatelymidway of its length, stationary contact means carried by the wall ofsaid chamber in position for cooperation with said movable contactmember, a. thrust member extending to the exterior of said housing andextending interiorly of said chamber intoposition for cooperation withthe other of said spring sections approximately midway of its length, amember aligned with said thrust member and adapted to be engaged by saidlast named spring section when said thrust member is actuated to flattensaid section, and a spring cooperating with said last named member andtensioned when the curvature of said second spring section is reversedby operation of said thrust member, reversal of curvature of said secondspring section effecting reversal of curvature of said first springsection to move said movable contact member abruptly relatively to saidstationary contact means and said second named spring automaticallyrestoring the curvature of said spring sections when pressure isreleased on said thrust member.

LOUIS M. PUSTER.

